A Chemical Sensor Based on AlGaN

Abstract:

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There is a particular interest in the development of wide band gap semiconductor gas
sensor because of their potential for high temperature operation and the ability to integrate them
with power or microwave electrodes or with UV solar-blind detector and emitters fabricated in the
same materials. AlGaN based devices are attractive for gas sensing in automotive exhausts and
flow-gas, because of strong spontaneous polarization of AlGaN (free carrier concentration profiles
inside this material that is very sensitive to any manipulation of surface change). In this report, we
characterized the Ni/AlGaN/Sapphire Schottky barriers as hydrogen gas sensor at temperature
range of 25°C to 500°C. A change in forward current was obtained in response to a change in
ambient from pure N2 to 2% H2/ 98% N2, higher than the change in forward current obtained in
Ni/GaN or Ni/Si Schottky diodes measured under the same conditions. The sensor response time
was independent on the rate of mass transport of gas into the test chamber, while at high
temperature, dissociation of gas controlled by the diffusion of atomic hydrogen through the
metal/AlGaN surface, increased the sensor response time.